U.S. patent application number 13/486107 was filed with the patent office on 2012-09-20 for synthesized hybrid rock composition, method, and article formed by the method.
Invention is credited to Ian I. Chang, Carl E. Frahme, ROSS GUENTHER, Robert D. Villwock, James L. Wood.
Application Number | 20120235320 13/486107 |
Document ID | / |
Family ID | 37772136 |
Filed Date | 2012-09-20 |
United States Patent
Application |
20120235320 |
Kind Code |
A1 |
GUENTHER; ROSS ; et
al. |
September 20, 2012 |
SYNTHESIZED HYBRID ROCK COMPOSITION, METHOD, AND ARTICLE FORMED BY
THE METHOD
Abstract
The invention relates to synthetic hybrid rock compositions,
articles of manufacture and related processes employing mineral
waste starting materials such as mine tailings, mine development
rock, ash, slag, quarry fines, and slimes, to produce valuable
articles of manufacture and products, which are characterized by
superior physical and structural characteristics, including low
porosity, low absorption, increased strength and durability, and
retained plasticity. The resulting materials are compositionally
and chemically distinct from conventional synthetic rock materials
as demonstrated by scanning electron microprobe analysis, and are
useful in a wide variety of applications, particularly with respect
to commercial and residential construction.
Inventors: |
GUENTHER; ROSS; (Penn
Valley, CA) ; Wood; James L.; (Colfax, CA) ;
Frahme; Carl E.; (Grass Valley, CA) ; Chang; Ian
I.; (North Vancouver, CA) ; Villwock; Robert D.;
(Austin, TX) |
Family ID: |
37772136 |
Appl. No.: |
13/486107 |
Filed: |
June 1, 2012 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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12767784 |
Apr 26, 2010 |
8216955 |
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13486107 |
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11213218 |
Aug 25, 2005 |
7704907 |
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12767784 |
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Current U.S.
Class: |
264/210.6 ;
425/378.1 |
Current CPC
Class: |
C04B 2235/6021 20130101;
Y02P 40/60 20151101; C04B 33/326 20130101; C04B 2235/3454 20130101;
C04B 2235/3262 20130101; C04B 2235/3201 20130101; C04B 28/021
20130101; C04B 2235/6567 20130101; Y02W 30/91 20150501; C04B 33/323
20130101; C04B 2235/3445 20130101; C04B 2235/448 20130101; B29C
48/793 20190201; C04B 2235/77 20130101; C04B 33/1352 20130101; C04B
2235/72 20130101; Y02W 30/92 20150501; B29C 48/832 20190201; C04B
2235/3208 20130101; C04B 2235/3232 20130101; C04B 2235/36 20130101;
C04B 2235/726 20130101; C04B 2235/721 20130101; C04B 28/14
20130101; B09B 3/005 20130101; Y02W 30/94 20150501; B29C 48/91
20190201; B28B 1/54 20130101; Y02W 30/93 20150501; C04B 2235/3234
20130101; C04B 2235/786 20130101; C04B 2235/96 20130101; C04B
2235/80 20130101; Y02P 40/69 20151101; C04B 2111/00129 20130101;
C04B 2235/3272 20130101; C04B 2235/3206 20130101; C04B 2235/3436
20130101; B29C 48/916 20190201; C04B 2235/6565 20130101; B29C 48/06
20190201; C04B 2235/3463 20130101; C04B 2235/447 20130101; C04B
28/021 20130101; C04B 18/06 20130101; C04B 18/12 20130101; C04B
18/141 20130101; C04B 40/0071 20130101; C04B 40/0089 20130101; C04B
40/0268 20130101; C04B 28/14 20130101; C04B 18/06 20130101; C04B
18/08 20130101; C04B 18/12 20130101; C04B 18/141 20130101; C04B
40/0071 20130101; C04B 40/0089 20130101; C04B 40/0268 20130101 |
Class at
Publication: |
264/210.6 ;
425/378.1 |
International
Class: |
B29C 47/78 20060101
B29C047/78 |
Claims
1.-47. (canceled)
48. A process for converting a material comprising a silicate waste
material into an article, comprising: heating the material to
partially and not completely melt the material; pressurizing the
material; extruding the material; and forming the article while
deformable.
49. The process of claim 48 wherein the waste material is heated
and pressurized within a heated chamber at a first temperature with
a first amount of pressure over a first period of time.
50. The process of claim 49 wherein the waste material is heated
and pressurized within said heated chamber at a temperature of
approximately 1130 degrees C. over a time period of approximately
60 hours.
51. The process of claim 49 wherein during heating the waste
material is pressurized at a pressure of approximately 350 psi.
52. The process of claim 49 wherein the waste material is cooled at
an approximate rate of 1 to 3 degrees per minute.
53. The process of claim 49 wherein the waste material is heated
and pressurized within said heated chamber at a temperature of
approximately 1140 degrees C. over a time period of approximately 6
hours.
54. The process of claim 53 wherein during heating the waste
material is pressurized at a pressure of approximately 300 psi.
55. The process of claim 53 wherein the waste material is cooled at
an approximate rate of 10 to 20 degrees per minute.
56. The process of claim 49 wherein the waste material is heated
and pressurized within said heated chamber at a temperature of
approximately 1160 degrees C. over a time period of approximately
60 minutes.
57. The process of claim 56 wherein during heating the waste
material is pressurized at an oscillating pressure between
approximately 30 psi and 160 psi.
58. The process of claim 56 wherein the waste material is cooled at
a rate of approximately 5 to 15 degrees C. per minute.
59. The process of claim 57 wherein the waste material is subjected
to said oscillating pressure in a partial vacuum environment.
60. The process of claim 49 wherein the waste material is heated
and pressurized within said heated chamber at a temperature of
approximately 1115 degrees C. over a time period of approximately
10 hours.
61. The process of claim 60 wherein during heating the waste
material is pressurized at a pressure of approximately 300 psi.
62. The process of claim 60 wherein the waste material is cooled at
a rate of approximately 10 to 20 degrees C. per minute.
63. The process of claim 49 wherein said hybrid rock is extruded
through a die.
64.-78. (canceled)
79. An apparatus for forming a synthetic hybrid rock comprising: a
preheater configured to preheat a silicate waste material; a feeder
configured to feed the silicate waste material into a heated
chamber; a heater configured to heat said heated chamber; and an
extruder configured to deliver the synthetic hybrid rock from an
exit of said heated chamber.
80. The apparatus of claim 79 wherein said preheater comprises a
heated rotating chamber maintained at a temperature to preheat and
dry the silicate waste materials without melting the silicate waste
material.
81. The apparatus of claim 80 wherein said heated rotating chamber
is situated at an angle to facilitate driving the silicate waste
material toward a discharge assembly.
82. The apparatus of claim 80 wherein said heated rotating chamber
comprises a gas inlet and a vent for the respective entry and
removal of air and/or other gases.
83. The apparatus of claim 80 wherein said temperature of said
heated rotating chamber is approximately 800 to 1000 degrees C.
84. The apparatus of claim 80 wherein said feeder comprises a dual
capacity press assembly.
85. The apparatus of claim 79, further comprising a vacuum.
86. The apparatus of claim 79 wherein said heater comprises a
heating element substantially surrounding said heated chamber.
87. The apparatus of claim 86 wherein said heating element
comprises a split-tube and multiple temperature zones.
88. The apparatus of claim 79, wherein the apparatus is configured
to cool the synthetic hybrid rock at a rate of approximately
between 1 and 30 degrees/minute.
89. The apparatus of claim 79 wherein said extruder comprises a
pressure resistance device configured to consolidate said synthetic
hybrid rock material; and a die device with an aperture configured
to allow said synthetic hybrid rock material to pass through.
90. The apparatus of claim 79, wherein the silicate waste material
is selected from the group consisting of mine tailings, mine
development rock, fly ash, bottom ash, slag, quarry fines, and
slimes.
Description
FIELD OF THE INVENTION
[0001] The following invention is generally directed to synthetic
hybrid rock compositions of matter, articles of manufacture and
related processes employing as starting material mine tailings,
mine development rock, ash, slag, quarry fines, slimes, and similar
mineral waste materials.
DESCRIPTION OF RELATED ART
[0002] Mine reclamation and waste mineral processing are not, by
far, new industries. Numerous systems, processes and methods exist
to affect environmental mine clean-up, and manufacture useful
products from raw materials comprised primarily of waste minerals
constituents.
[0003] U.S. Pat. No. 3,870,535 discloses a method of treating coal
mining refuse to produce a cementitious material, which is
self-hardening at atmospheric pressure, and may be used as
structural fill, road base material, or alternatively as an
aggregate consolidated barrier to prevent penetrating percolation
and resulting surface water contamination. The method involves
treating coal mining tailings from coal extraction processes with
lime (to neutralize sulfuric acid), or lime and a pozzolanic
material, such as fly ash, to react at atmospheric pressure for at
least several days, in the presence of moisture with sulfate ions
that have been released from the tailings, and in some cases also
to react with soluble iron products in the tailings. The claimed
products are admixtures of coal mining refuse and
stoichiometrically distinct concentrations of lime, water and fly
ash. The products of the invention are generally of the variety
3CaO, Al.sub.2O3, 3CaSO.sub.4, 30-32H.sub.2O or 3CaO,
Al.sub.2O.sub.3, CaSO.sub.4, and 10-12H.sub.2O. Permeability
testing data for product samples indicated that permeability
diminished after completion of a seven day curing period at
100.degree. F. Likewise, compressive strength data indicated that
the material's compressive strength, measured in PSI, increased as
the curing period progressed. Detailed information regarding the
composition's density and plasticity is not disclosed. However, the
composition is cementitious in nature, and therefore limited in
application and potential utility. Well known disadvantages
associated with cement based products include high porosity and
structural instability as a result of temperature and climate
fluctuations.
[0004] U.S. Pat. No. 5,286,427 discloses a method of effecting
environmental cleanup by producing structural building materials
using mine tailings waste material. The method involves providing
facilities for producing the structural building material;
providing raw materials for producing the building material, the
raw materials comprising unprocessed mine tailings (with a material
gradation suitable for immediate use) as a substitute for processed
silica sand, plus cement and aluminum powder; analyzing the mine
tailings to determine composition and weight percentage amounts of
other raw materials present; preparing a slurry from the mine
tailings and combining the slurry with other raw materials to form
a batch slurry; adjusting amounts of other raw materials in
accordance with determined weight percentage amounts in the mine
tailings; and processing the batch slurry through the provided
facility, including a final curing step that produces the building
structural material. Due to the chemical reaction that takes place
in the casting stage, the production slurry changes from a fluid
form to a quasi-solid form of the building material. The
quasi-solid form expands and conforms to a mold shape and
facilitates being cut into smaller units prior to curing. The
autoclaved aerated cement, as produced and claimed, is of limited
utility because the composition lacks plasticity and is therefore
incapable of efficient subsequent reformation. Information
regarding the material's permeability, porosity, and required
curing time period are not disclosed. As previously stated, well
known disadvantages associated with cement include high porosity
and structural instability as a result of temperature and climate
fluctuations.
[0005] U.S. Pat. No. 6,825,139 discloses a crystalline composition,
a poly-crystalline product, an article of manufacture, and a
related process utilizing coal ash as starting material. The
process involves mixing coal ash particles with at least one glass
forming agent and at least one crystallization catalyst, melting
this combination to form a mixture, and cooling the resulting
mixture to ambient temperature to form a homogenous, non-porous
poly-crystalline product comprising SiO.sub.2, Al.sub.2O, CaO,
Fe.sub.2O.sub.3, TiO.sub.2, MgO, Na.sub.2O, Li.sub.2O, CeO.sub.2,
ZrO.sub.2, K.sub.2O, P.sub.2O.sub.5, Cr.sub.2O.sub.3, ZnO and
MnO.sub.2. The poly-crystalline products are poly-crystalline
materials obtained from glass compositions by means of catalysis
crystallization and consisting from one to several crystalline
mineralogical phases uniformly distributed in the remaining glass
phase. Microstructure assessment, as revealed by electron
microscopy, showed a dense glass-ceramic structure with crystal
dimensions approximately 1 .mu.m. The composition's mineralogical
composition, as demonstrated by X-ray diffraction, revealed that
the predominant crystalline phase is anorthite, whereas additional
crystalline phases include albite and lithium disilicate. The glass
density was found to be up to 2720 kg/m.sup.3; the porosity less
than 0.02%; and bending strength was up to 150 MPa. However, the
composition is heated to temperatures that require addition of at
least one crystallization catalyst to effect the various
crystalline phases, and to that extent the composition, article and
corresponding process are relatively cumbersome and prone to
inaccuracy should mistakes occur during catalyst addition.
[0006] Bulk processing of relatively homogeneous mined mineral
material has also resulted in the creation of numerous ceramic tile
products of varying quality and durability. For instance,
conventional ceramics produced by processing mixtures of natural
mineral constituents and admixtures can be classified according to
their glass content as non-vitreous, semi-vitreous, and vitreous.
Non-vitreous ceramic, of which Dal-Tile is an example, is generally
manufactured from clay, talc, and carbonate minerals, and has water
absorption greater than about 7%. No fluxing minerals such as
feldspar are used in these compositions. Non-vitreous Dal-Tile of
this type has a water absorption of 13-14%, as measured by ASTM
C373. This type of tile has virtually no glass content, and gets
its structural integrity from solid-state reactions and sintering.
Semi-vitreous ceramic, of which Balmor is an example, generally has
some glass content and corresponding water absorption between about
4% and about 7%. This is a red body product, its color due to its
natural iron content. Such bodies are often made of natural
clay-containing earth mixtures which contain natural quartz and
feldspar. The latter acts as a fluxing agent to produce a liquid
phase during firing, said liquid phase converting to glass during
cooling. Vitreous ceramic, including porcelain tile, of which
Granitifiandre. Kashmir White is an example, has less than 4% water
absorption. True porcelain products typically have water absorption
values less than about 0.5%. These materials are primarily produced
from the raw materials kaolinite clay, quartz, and feldspar. They
have a high glass content (typically 20-30%), and are also
characterized by a lack of crystalline phases that have
precipitated from the melt during cooling. They often contain the
mineral mullite (3Al.sub.2O.sub.3-2SiO.sub.2) formed at elevated
firing temperatures from solid state decomposition of the kaolinite
raw material.
[0007] Commercially Available Ceramic-Tile
Materials--Non-Vitreous
[0008] FIG. 1 is the scanning electron microprobe back-scattered
electron (BSE) image of the non-vitreous commercial ceramic tile
manufactured by Dal-Tile.TM.. This BSE image illustrates the
typical microfabric of this non-vitreous ceramic tile dominated by
discrete flaky particles (1 and 2) that are cemented (sintered)
with no apparent glass matrix. The Energy Dispersive X-ray (EDX)
microchemical analysis spectra of the dominant flaky particles show
a magnesium-silicate chemistry. This composition corresponds with
the mineral "enstatite" (MgO--SiO.sub.2) identified in the X-ray
diffraction analysis (XRD) performed on this ceramic tile sample.
The enstatite mineral phase did not "grow" or crystallize out of a
melt, since none exists, but instead was formed as a high
temperature pseudo-morphous solid state replacement mineral for an
original largely talc feedstock material. Talc is a hydrated
magnesium silicate mineral Mg.sub.3Si.sub.4O.sub.10(OH).sub.2).
[0009] Light colored (white) reaction rims (3) surround voids
(black), some of which contain partially dissolved particles (4).
EDX analysis indicates that the rims (3) possess a magnesium
aluminum silicate chemistry that corresponds with the mineral
cordierite (MgO--Al.sub.2O.sub.3--SiO.sub.2) detected by XRD
analysis. The partially dissolved particles in the center of some
of the voids have a magnesium oxide chemistry typical of periclase.
The abundance of this MgO material was too low to be detectable in
XRD analysis.
[0010] Minor angular particles (5) with a silica chemistry
corresponds to the composition of quartz (SiO.sub.2) detected as a
minor component in this ceramic tile by XRD analysis.
[0011] The abundant void space (black) illustrates the high
porosity of this non-vitreous ceramic tile material (6). The
absence of significant glassy matrix in this material causes poor
grain-to-matrix bonding contact (7). Both of these physical
properties contribute to greater water absorption, lower hardness
and lower modulus of rupture (MOR--a measure of mechanical
strength) determined for this ceramic tile.
[0012] Commercially Available Ceramic-Tile
Materials--Semi-Vitreous
[0013] FIG. 2 is the scanning electron microprobe back-scattered
electron (BSE) image of the Balmor.TM. semi-vitreous commercial
ceramic tile. FIG. 2 illustrates the typical microfabric of this
semi-vitreous ceramic tile comprised of partially to completely
dissolved primary mineral grains. EDX analyses of these mineral
grains revealed the chemical compositions, which correlate to the
specific minerals identified by XRD analysis as being constituents
of this tile material. These include potassium-feldspar (10),
plagioclase feldspar (11), quartz (12) and goethite (Fe(OH).sub.2)
(13).
[0014] These primary mineral grains are cemented by a
semi-continuous amorphous glass matrix. The EDX microchemical
analysis of two glassy matrix areas (14 and 15) shows that the
particular ratios of the cations K, Na, and Ca in the two glassy
areas appear to be similar to the two adjacent feldspar
compositions (compare 10 with 14 and 11 with 15). This similarity
indicates that glass compositions may vary with respect to the
cation composition, and are influenced by the specific cation
constituents within the adjacent mineral grains that melt or
dissolve to form the glass matrix material.
[0015] FIG. 2 reveals that the glassy matrix of this semi-vitreous
ceramic tile is semi-continuous resulting in a moderate degree of
retained porosity 16. This porosity is largely, but not completely,
unconnected resulting in lower water absorption properties. The
primary grains are not entirely bonded (17) to the glassy matrix
which causes a reduction in the durability and hardness of the
material.
[0016] FIG. 2 also shows no secondary crystallite minerals within
the glassy matrix. No evidence is indicated that new crystalline
mineral phases have precipitated from the melt during the cooling
process.
[0017] Commercially Available Ceramic-Tile Materials--Vitreous
[0018] FIG. 3 is the scanning electron microprobe back-scattered
electron (BSE) image of the Granitifiandre Kashmir White vitreous
porcelain ceramic tile. This BSE image illustrates the typical
microfabric of this vitreous ceramic tile comprised of remnants of
partially dissolved primary grains. The EDX microchemical analysis
of some of these grains correlates with the XRD analysis to confirm
that the mineralogy of this ceramic tile is dominated by quartz
(20), plagioclase feldspar (21) and zircon (22).
[0019] FIG. 3 reveals that the quartz grain boundaries show
evidence of significant dissolution (20) while the feldspar grains
are severely to completely melted or dissolved (21). The minor
zircon grains were evidently an admixture to achieve a mottled
texture in the porcelain tile body (surface 22). The glassy matrix
appears to be continuous, leaving only a few isolated voids or
pores and producing low water absorption properties (23).
[0020] FIG. 3 also shows no apparent secondary crystallite minerals
within the glassy matrix and suggests that no such secondary
minerals formed from the melt. However, mullite--a mineral formed
through solid state transformation from kaolinite--was identified
in XRD analysis. Because of its typical needle-shaped crystal shape
and very small particle size, its presence in this ceramic was not
positively identified in the BSE analysis. The total atomic weight
(density) of mullite may be too similar to the glass matrix
rendering it indistinguishable from the glass.
[0021] As discussed above, inefficiencies involving conventional
methods of processing waste minerals such as mine tailings, and the
structural and compositional limitations inherent in conventional
ceramic products--particularly with respect to porosity and
corresponding water absorption, diminished hardness and low modulus
of rupture--demonstrate that a dual need exists for: (1) an
effective and efficient strategy to reclaim mineral wastes such as
mine tailings at low cost and high safety; and (2) a low cost and
easily manufactured non-clay vitreous synthetic rock material with
superior, and heretofore collectively unavailable, characteristics
including low porosity; impermeability without glazing;
high-plasticity for subsequent reformation; and high strength and
durability. The disclosed invention addresses these dual needs
simultaneously.
BACKGROUND OF THE INVENTION
[0022] Mine tailings and mine reclamation efforts have evoked
enormous environmental concerns in the United States and abroad.
Tailings are waste products remaining in containment areas or
discharged to receiving waters after metals are extracted from a
particular site, and consist primarily of waste rock containing a
variety of rock forming minerals, including as major constituent
groups crystalline silica, feldspars and clay minerals; with minor
constituent groups including carbonates, sulfates, sulfides and
micas. Pollution issues associated with mine tailings relate to the
structural integrity and stability of tailings containment areas
and the potential for pollution impacts should containment failure
occur. At the heart of these concerns is the pollution potential of
mine tailings on ground and surface water, and correspondingly how
such potential pollution affects people living in the immediate
vicinity of tailings containment areas.
[0023] The need for effective mine reclamation strategies, and safe
disposition of potentially hazardous mine tailings, is widely
recognized in the mining and environmental industries alike. There
is no legitimate doubt that disposing of mine tailings in a safe
manner, as opposed to continually attempting their containment, is
desirable from both an environmental safety and economic point of
view. Likewise, other mineral waste materials raise similar
environmental contamination concerns, and the need for their safe
and effective disposition is also well acknowledged.
[0024] As far back as ancient Mesopotamia, researchers have located
what they believe to be basalt rock slabs formed from silt. It is
believed that inhabitants used the basalt rock as a main staple in
the region for a variety of purposes, including pottery,
architecture, writing materials, art objects and tools. In
simulation studies to recreate the basalt rock from silt,
researchers were able to approximate the composition and texture of
the basalt rock using local alluvial silt as raw starting material,
and heating the material within a defined temperature range over a
sustained time period. The resulting basalt rock was characterized
by matted clinopyroxene crystals embedded in a glassy matrix, with
starting material remnants either rarely appearing in, or
completely absent from, the final basalt rock. The basalt rock was
most likely of limited strength, as it lacked an aggregate
microstructure. Due to the observed presence of many large pores,
some as big as 3 mm, the basalt had high water absorption, likely
well in excess of 7%.
[0025] In more recent examples of waste materials, fly ash and
bottom ash from burning coal for electric power are largely
incombustible residuals formed from inorganic minerals in coal.
Roughly hundreds of million tons is produced every year in the USA
alone. Fly ash and bottom ash are also produced in waste
incinerators and biomass-fueled power plants. Slag mineral waste
materials result from metal processing operations. Quarry and
dredging operations often produce silicate waste materials such as
fines or slimes that must be disposed of in a safe manner.
[0026] Relatively pure mineral materials (kaolinite clay, feldspar,
quartz, talc, etc.) have conventionally been used to manufacture a
variety of ceramic materials with varying compositions and degrees
of quality. As previously described, non-vitreous Dal-Tile,
semi-vitreous Balmor Tile and vitreous Granitifiandre Kashmir White
tile represent a very few. However, these and a vast array of other
conventional ceramic products (ceramic tile, dinnerware,
sanitaryware, etc.) are typically manufactured by methods that rely
on the plasticity and bonding (in the unfired state) of
clay--largely kaolinite--and generally use relatively pure raw
materials. As previously stated, conventional ceramics also
demonstrate a number of undesirable characteristics,
including--moderate to high porosity and water absorption, low
hardness and strength, and the absence of secondary crystallite
formation upon cooling, which contributes to product durability.
Also, in the manufacture of conventional ceramics, considerable
concern is placed on the quality and purity of the raw material
ingredients. Further, contaminants in the raw materials can cause
considerable damage to the quality of the conventional product in
terms of structural integrity and defects in the cosmetic
properties. Surprisingly, Applicant's process and composition are
tolerant of higher concentrations of many materials that are
considered contamination in conventional ceramics manufacture. Such
materials include iron, magnesium, manganese, sulfur, and their
compounds.
[0027] The need exists in the environmental clean-up industry to
develop an effective and efficient strategy for reclaiming mines,
disposing of mine tailings after mineral extraction at the mine is
complete, disposing of mine development rock, disposing of fly ash
and bottom ash from power plants or incinerators, disposing of
slag, and disposing of fines or slimes. An equally significant need
exists in the synthetic rock industry to produce a low porosity,
easily manufactured, low absorption vitreous tile in a cost
effective and relatively fast manner.
SUMMARY OF THE INVENTION
[0028] The applicant's invention provides a crystalline and glass
composition derived from processing raw mine tailings and similar
waste materials, which can be used to create valuable articles of
manufacture and products for a wide variety of uses, particularly,
but without limitation, in the commercial and residential
construction industry, for example floor, wall, and roof tile,
brick, blocks, siding, panels, pavers, countertops, aggregates for
road base, and other building materials. The unique composition
comprises a clast phase, a glass phase, and a crystalline phase.
Said clast phase is further comprised of mineral grains, mineraloid
grains, glass spherules, or rock fragments, any of which may have
been partially melted, or partially dissolved, or partially
transformed by chemical reaction. Said glass phase provides a
matrix that cements together the clasts. Said crystalline phase is
fully enveloped by the glass phase, having formed by growth from
the melt. The unique composition of clasts fused together by a
unique glass phase, which further comprises a newly formed
crystalline phase, is characterized by a microscopic aggregate
breccia (synthetic rock/glass matrix) structure with superior
physical and structural characteristics, including low porosity,
low absorption, increased strength and durability, retained
plasticity to facilitate reformation subsequent to initial
processing, and readily distinguishable chemical attributes in
comparison to conventional synthetic rock materials, as
demonstrated by scanning-electron-microprobe analysis.
[0029] The glass phase (glass matrix) is created as a result of
partially melting a suite of original raw mineral constituents,
which may include feldspar, quartz and mineral materials found in a
wide variety of rock types, and which further may be present as
individual mineral grains (monomineralic) or as rock fragments
(polymineralic). After an optimal melting period, the resulting
glass matrix is cooled over an optimal cooling period, and during
the cooling period unique silicate and non-silicate minerals with
varying proportions of iron, magnesium, calcium and sulfur
crystallize from the melt to form small crystallites distributed
throughout the glass matrix. Importantly, the newly formed
secondary crystallites include specific inosilicate, tectosilicate
and sulfate compounds that are not present in the starting raw
material, and are not found in commercially-available ceramics in
the same fashion. Occasionally, some of these minerals may be found
in commercially-available ceramics; however those minerals are not
secondary crystallites formed from a melt phase, but rather are
remnants of the raw starting material. The specific minerals formed
in applicants ceramic materials are influenced by the unique
chemistry of the waste mineral feedstock materials such as
tailings, ash, etc.
[0030] Inosilicates are single-chain and double-chain silicate
minerals. The Pyroxene Group of inosilicates comprises
single-chain, non-hydrated ferromagnesian chain silicates. The
Amphibole Group of inosilicates comprises double-chain, hydrated
ferromagnesian chain silicates. Wollastonite is a calcium silicate
mineral in the inosilicate group.
[0031] Tectosilicates are framework silicate minerals, including
minerals such as quartz and the Feldspar Group. Plagioclase
feldspar is a solid solution series of feldspar minerals with
varying amounts of sodium and calcium.
[0032] Sulfate minerals are a group of minerals containing sulfur.
Gypsum and anhydrite are calcium sulfates, with anhydrite forming
the dehydrated form and gypsum the hydrated form.
[0033] Pyroxenes, particularly enstatite and hypersthene (the iron
containing version of enstatite), as well as augite, diopside,
bronzite, and pigeonite, are not conventionally present in raw
starting materials, and have not been detected in vitreous,
semi-vitreous or porcelain ceramics. Rather, pyroxenes have been
detected, via X-Ray Diffraction analysis (XRD) and Scanning
Electron Microprobe analysis (microprobe) using an Energy
Dispersive X-ray Spectrometer (EDS), only in high porosity
ceramics, such as the non-vitreous ceramic Dal-Tile discussed
above. However, microprobe analysis reveals that those pyroxenes in
the non-vitreous ceramic have a morphology that indicates to one
skilled in the art that they are the result of solid-state chemical
reactions rather than crystallization from a melt phase.
Conversely, amphiboles, particularly in the form of hornblende,
have been detected in raw mine rock materials, but not in processed
material, because these compounds do not survive high temperature
processing as a result of dehydration and bond degradation during
the heating process.
[0034] Wollastonite and plagioclase are common ingredients of some
non-vitreous conventional ceramics to achieve specific ceramic
types and properties. However, wollastonite and plagioclase have
not been detected using microprobe analysis and EDS techniques as a
newly crystallized phase in conventional ceramics, rather they
appear as sintered primary mineral grains.
[0035] Anhydrite and/or gypsum are not conventionally present in
raw starting materials, and have not been detected in conventional
non-vitreous, semi-vitreous or vitreous ceramics.
[0036] Applicant's compositions and articles of manufacture
comprise both original tailings fragments as well as newly formed
mineral phases, which renders them compositionally distinct not
only from the raw mine tailings starting material, but--more
importantly--from conventional synthetic rock compositions and
corresponding articles of manufacture. A key compositional
distinction between the raw starting material, applicant's
compositions and articles, and conventional synthetic rock
compositions is the presence or absence of inosilicate minerals,
specifically pyroxenes, wollastonite, tectosilicates, specifically
plagioclase feldspar, and sulfates, specifically anhydrite. As more
fully set forth below, applicant's compositions and articles
contain pyroxene inosilicates, newly formed plagioclase,
wollastonite and anhydrite, which heretofore have not been detected
in low porosity, vitreous synthetic rock materials. Specific
pyroxene minerals that may form in this synthetic rock may include,
but are not limited to, one or more of the following: augite,
diopside, hypersthene, pigeonite, bronzite and enstatite.
[0037] In addition, applicant's invention employs a unique heating
and cooling strategy, which completely obviates the need for the
addition of crystallization catalysts. That is, heating of the raw
material to a temperature at which some, but not all, of the
components of the raw material begin to at least partially melt. At
these temperatures, a liquid phase is created that can flow to coat
individual aggregate particles, bind them together, and fill in
void spaces. The liquid phase can also begin to dissolve additional
solid material. Upon cooling at reasonable unquenched rates, this
liquid phase can partially crystallize without the need for
addition of nucleation additives because, due to partial melting,
there are already present solid surfaces to initiate
crystallization. Mechanical pressure to squeeze the material at
temperature can help to distribute the liquid phase among the
various solid surfaces and increase binding. Vacuum to remove gas
from void spaces can help to eliminate resistance to filling in the
voids with the liquid phase.
[0038] Typically the first components of the raw material to
liquefy are glass particles or feldspars, many of which liquefy at
temperatures of approximately 1050 to 1300 degrees C. Preferably,
the raw material comprises glass or feldspar that becomes liquid at
temperatures in the range of 1100 to 1200 degrees C. Cooling from
these temperatures preferably takes place at a rate slow enough to
allow crystallization to occur, preferably about 1 to 50 degrees C.
per minute, more preferably about 5 to 20 degrees C. per minute,
and most preferably about 10 degrees C. per minute when cooling is
initiated from the peak temperature for the first few hundred
degrees of cooling. Cooling at a maximum rate of 10 degrees C. per
minute is also especially preferred as the material passes through
the temperature range of 600 to 500 degrees C., to avoid fracture
due to the associated volume change of the beta-to-alpha phase
transition of any quartz that may be present in the material.
[0039] In the embodiments and examples of the present invention
that follow, an amount of mine tailings, for example Historic
Idaho-Maryland Mine Tailings ("HIMT"), containing both rock
fragments and individual mineral grains, is heated in a forming
chamber to an optimal temperature, preferably in the range of 1100
to 1200 degrees C., and thereby partially melted over an optimal
period of time, preferably about 0.5 to 6 hours. During the partial
melting process, the HIMT raw material is simultaneously exposed to
pressure modification, which preferably is the application of
mechanical force to the material in the range of 1 to 200 psi, and
which further may also be the application of vacuum to reduce the
absolute pressure to within the range of about 1 to 600 mbar in
order to remove interstitial gas phase.
[0040] Heating the HIMT raw material with pressure modification
results in a partially melted matrix, which is then allowed to cool
over an optimal period of time. During the cooling period, newly
formed mineral crystallites with varying proportions of silicon,
aluminum, iron, magnesium, calcium, and sulfur crystallize from the
initial raw material melt to form small crystallites distributed
throughout a glass matrix. As previously stated, the invention does
not employ added crystallization catalysts or nucleating agents to
facilitate the crystallization process.
[0041] The newly formed crystallized minerals occurring in the
glass matrix comprise a combination of minerals from the Pyroxene
Group, Plagioclase Feldspar Group and Sulfate Group. Morphological
characteristics of the newly crystallized minerals indicate their
secondary growth from the initial raw material melt, as opposed to
from a solid state glass reaction. Most notably, these secondary
growth indicators include the newly formed minerals' generally
uniform size, crystalline morphology and uniform composition
throughout the glass matrix.
[0042] In one embodiment, the invention provides a vitreous,
non-porous, impermeable polycrystalline composition comprising an
amount of clasts, an amount of glass matrix, and an amount of at
least one secondary crystalline phase. Said clasts comprise grains
of single minerals, such as quartz, or rock fragments, or unmelted
glass fragments, or mineraloid grains. Said glass matrix is
distributed between the clasts, bonding to them and filling in the
nearly all of the interstitial space. Said at least one secondary
crystalline phase is contained within the glass matrix, and is
comprised of crystals formed from a melt with a mineral composition
selected from the group consisting of ferromagnesian minerals,
pyroxenes (for example, clinopyroxene, orthopyroxene, augite,
diopside, hypersthene, pigeonite, bronzite, enstatite), illmanite,
rutile, wollastonite, cordierite, and anhydrite.
[0043] In one embodiment, the invention provides a method for
processing mine tailings resulting in a vitreous, non-porous,
impermeable polycrystalline composition. Said method comprises air
drying a sampling of mine tailings to less than 3% moisture;
screening the mine tailings to remove material larger than 516
microns; and calcining the mine tailings in air at approximately
900 degrees C. The mine tailings are then mechanically compacted in
a tube with an approximate pressure of 350 psi at an approximate
temperature of 1130 degrees C. for approximately 60 hours, and
subsequently cooled at a rate of approximately 1 to 3 degrees C.
per minute, forming said composition, comprising a clast phase, a
glass phase, and at least one crystalline phase. Said clast phase
comprises grains of single minerals, such as quartz, or rock
fragments. Said glass phase is distributed between said clast
phase, bonding to clast particles and filling in nearly all
surrounding interstitial space. Said at least one crystalline phase
is contained within said glass phase, and comprises crystals formed
from a melt with a mineral composition consistent with minerals
selected from the group consisting of bronzite, augite and
pigeonite.
[0044] In another embodiment, the invention provides a method for
processing mine tailings resulting in a vitreous, non-porous,
impermeable polycrystalline composition. Said method comprises
drying a sampling of mine tailings to less than 3% moisture;
screening the mine tailings to remove material larger than 516
microns; and calcining the mine tailings in air at approximately
900 degrees C. The mine tailings are then mechanically compacted in
a tube with an approximate pressure of 300 psi at an approximate
temperature of 1140 degrees C. for approximately 6 hours, and
subsequently cooled at a rate of approximately 10 to 20 degrees C.
per minute, forming said composition, comprising a clast phase, a
glass phase, and at least one crystalline phase. Said clast phase
comprises grains of single minerals, such as quartz, or rock
fragments. Said glass phase is distributed between said clast
phase, bonding to clast particles and filling in nearly all
surrounding interstitial space. Said at least one crystalline phase
is contained in said glass phase and comprises crystals formed from
a melt with a mineral composition consistent with minerals selected
from the group consisting of bronzite, augite, pigeonite, anhydrite
and ilmanite.
[0045] In another embodiment, the invention provides a method for
processing metavolcanic mine development rock resulting in a
vitreous, non-porous, impermeable polycrystalline composition. Said
method comprises air drying a sampling of the development rock to
less than 3% moisture; and screening the development rock through a
516 micron screen. Development rock powder is then processed
through the apparatus described in U.S. Pat. No. 6,547,550
(Guenther) at a temperature of approximately 1160 degrees C., with
mechanical pressure oscillating between approximately 30 psi and
160 psi for a defined time period, in a partial vacuum atmosphere
for approximately 60 minutes, and subsequently cooled at an
approximate rate of 5 to 15 degrees C. per minute, forming said
composition, comprising a clast phase, a glass phase and at least
one crystalline phase. Said clast phase comprises polymineralic and
monomineralic clasts. Said glass phase is distributed between said
clast phase, bonding to clast particles and filling in nearly all
surrounding interstitial space. Said at least one crystalline phase
is contained in said glass phase and comprises crystals formed from
a melt with a mineral composition consistent with minerals selected
from the group consisting of augite, pigeonite, maghemite and
ilmanite.
[0046] In another embodiment, the invention provides a method for
processing coal fly ash resulting in a vitreous, non-porous,
impermeable polycrystalline composition. Said method comprises air
drying a sampling of the coal fly ash to less than 3% moisture;
screening the coal fly ash with a 516 micron screen; and thereafter
calcining the coal fly ash. The coal fly ash is then mechanically
compacted at an approximate pressure of 300 psi in a tube at an
approximate temperature of 1115 degrees C. for approximately 10
hours, and subsequently cooled at an approximate rate of 10 to 20
degrees C. per minute, forming said composition, comprising a clast
phase, a glass phase, and at least one crystalline phase. Said
clast phase comprises remnant clasts from the original feedstock
constituents. Said glass phase is distributed between said clast
phase, bonding to clast particles and filling in nearly all
surrounding interstitial space. Said at least one crystalline phase
is contained in said glass phase and comprises crystals formed from
a melt with a mineral composition consistent with minerals selected
from the group consisting of wollastonite, plagioclase feldspar,
anhydrite, and calcium sulfate.
[0047] In another embodiment, the invention provides a method of
processing waste materials selected from the group consisting of
mine tailings, waste rock, quarry waste, slimes, fly ash, bottom
ash, coal ash, incinerator ash, wood ash, and slag, resulting in a
vitreous, non-porous, impermeable polycrystalline composition. Said
method comprises subjecting the waste materials to a screening
apparatus; conveying the waste materials from said screening
apparatus to a heated rotating chamber for chemical transformation;
conveying the waste materials from said heated rotating chamber to
a second heated chamber optionally fixed with a vacuum; conveying
the waste materials from said second heated chamber to a third
heated chamber positioned within a heating element; applying
pressure to the waste materials in said third heated chamber
forming a hybrid rock; extruding said hybrid rock through a die
device and removing said hybrid rock from said third heated chamber
for subsequent use or further modification.
[0048] The benefits, advantages and surprising discoveries
resulting from the present invention are, in a word, remarkable.
First and foremost, a surprising discovery regarding applicant's
invention is the presence of pyroxene inosilicates in the final
composition and corresponding articles. Heretofore, pyroxene
mineral compounds have not been detected in vitreous, low-porosity,
low absorption synthetic rock materials such as applicant's present
invention. Rather, pyroxenes have only been conventionally detected
in highly porous, non-vitreous materials.
[0049] Also surprising is the fact that applicant's invention
achieves maximum crystallization without the addition of
crystallization catalysts or other nucleating agents. The raw
material in applicant's invention is not heated beyond its melting
point, but rather is only partially melted, which preserves
crystallization nuclei sites already present in the glass matrix.
Conversely, conventional synthetic rock compositions must employ
crystallization catalysts to facilitate crystal formation because
corresponding raw materials are heated to above their melting point
and completely melted to a homogenous state during processing,
which destroys potential crystallization sites. Conventional
crystallization catalysis is required to provide a site for
crystallization.
[0050] Yet another surprising discovery regarding applicant's
invention is that the invention's glass matrix can comprise various
amounts of glass, but that with less than approximately 20% glass
the composition achieves impermeability. Conventional low or
non-permeable synthetic rock materials require a high glass content
to achieve impermeability.
[0051] The invention also has the advantage of providing
compositions of matter comprising crystalline particles within a
glass-binding liquid matrix, which allows the compositions to
maintain a significant amount of plasticity at high temperature,
unlike conventional clay tile. With this heightened plasticity
level the compositions can, while initially heated or re-heated, be
pressed, rolled or injected into other shapes and a variety of
useful products after initial preparation. For instance, fine
grained versions of the solid compositions can be pressed into
aggregates and cobbles for a variety of construction uses,
including for use in cement, road base and cobblestones.
Alternatively, commonly known abrasives, such as silica carbide,
quartz and garnet, can be added to the composition for subsequent
use in sanding blocks and grinding wheels.
[0052] Another advantage of the present invention is that the solid
compositions and corresponding articles of manufacture are
impermeable without the need for glazing. The invention's
impermeability is directly related to the fact that, unlike
conventional synthetic rock materials, the composition and articles
contain essentially zero open porosity, due to the continuous glass
matrix structure surrounding crystallites distributed throughout
therein. With the exception of certain rare vitreous expensive clay
products, such as porcelain, conventional synthetic rock and
ceramic products require glazing to achieve impermeability.
[0053] As previously stated, applicant's invention contains
virtually zero open porosity, which results in less porous and more
impermeable articles as compared to conventional ceramic materials.
Surprisingly, voids (closed pores) may be induced in applicant's
invention to result in a lighter weight construction-type material,
without compromising the invention's impermeable
characteristics.
[0054] Other aspects and alternatives or preferred embodiments of
the invention exist. They will become apparent as the specification
proceeds.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] FIG. 1 is a micrograph obtained from scanning electron
microprobe analysis of commercially available (Dal-Tile)
non-vitreous ceramic tile.
[0056] FIG. 2 is a micrograph obtained from scanning electron
microprobe analysis of commercially available (Balmor)
semi-vitreous ceramic tile.
[0057] FIG. 3 is a micrograph obtained from scanning electron
microprobe analysis of commercially available (Granitifiandre,
Kashmir White) vitreous ceramic tile.
[0058] FIG. 4 is a micrograph obtained from scanning electron
microprobe analysis of an article of manufacture resulting from
Applicant's method of processing mine tailings, including an
illustration of the article's composition.
[0059] FIG. 5 is a micrograph obtained from scanning electron
microprobe analysis of an article of manufacture resulting from
Applicant's method of processing mine tailings, including an
illustration of the article's composition.
[0060] FIG. 6 is a micrograph obtained from scanning electron
microprobe analysis of an article of manufacture resulting from
Applicant's method of processing mine development rock, including
an illustration of the article's composition.
[0061] FIG. 7 is a micrograph obtained from scanning electron
microprobe analysis of an article of manufacture resulting from
Applicant's method of processing coal fly ash, including an
illustration of the article's composition.
[0062] FIG. 8 is a schematic flowchart depicting an apparatus and
method of processing waste mineral materials.
DETAILED DESCRIPTION OF THE INVENTION
The First Embodiment
[0063] This embodiment is an apparatus and process for processing
mine tailings employing a slow cooling schedule, which results in
Applicant's composition and corresponding articles of
manufacture.
TABLE-US-00001 TABLE 1 Composition of some feed materials
Idaho-Maryland Idaho-Maryland mine tailings development rock coal
fly ash mass % mass % mass % loss on ignition 11.29 4.19 19.1 SiO2
55.6 48.7 39.84 Al2O3 9.89 14.8 13.23 Na2O 1.99 3.40 1.77 MgO 5.01
8.17 1.66 K2O 1.52 0.33 0.67 CaO 7.03 9.23 19.52 Fe2O3 5.12 9.72
2.62 MnO 0.11 0.15 0.02 P2O5 0.18 0.12 0.42 TiO2 0.67 0.93 0.62 C
(inorganic) 0.23 0.55 5.16 C (organic) 2.33 0.02 1.65 C (total)
2.56 0.57 6.81 S 0.41 0.16 3.86
Example 1
[0064] A sample of tailings from the Idaho-Maryland gold mine,
having the general composition shown in Table 1, was air-dried to
less than 3% moisture and screened to remove material larger than
516 microns (30 mesh). The raw tailings material was calcined in
air at 900 degrees C. Following calcining, the material, without
additives, was mechanically compacted using a ram at a pressure of
approximately 350 psi within a nitride-bonded-silicon-carbide
process tube at a temperature of 1130 degrees C. for an extended
period of time, approximately 60 hours at temperature. The material
was then slowly cooled, at a rate of 1 to 3 degrees C. per minute,
forming a synthetic rock hybrid material, which was then removed
from the process tube. Test specimens of the resulting synthetic
rock hybrid material had an average modulus of rupture of about 85
MPa (12320 psi), and an average water absorption of about 0.3% as
determined by method ASTM C373. Other resulting data are shown in
Table 2.
TABLE-US-00002 TABLE 2 Physical properties of example synthetic
rock hybrid materials. Ex. 1 Ex. 2 Ex. 3 Ex. 4 modulus of rupture
(psi) 12320 6060 9280 8230 apparent porosity (%) ASTM 0.7% 6.8%
2.3% 1.8% C373 water absorption (%) ASTM 0.3% 3.2% 0.8% 0.7% C373
apparent specific gravity ASTM 2.67 2.32 2.83 2.53 C373 bulk
density (g/cm3) ASTM 2.65 2.16 2.76 2.49 C373
[0065] FIG. 4 is the scanning electron microprobe back-scattered
electron (BSE) image of this synthetic rock hybrid material of
Idaho Maryland mine tailings feedstock. FIG. 4 illustrates the
three characteristic phases typical of the unique microfabric of
this synthetic rock material. These three phases include clasts
(partially dissolved remnant primary grains of the tailings
feedstock); a glass phase derived from the partial melting of
primary mineral grains; and a secondary crystalline phase comprised
of similarly sized crystallites that occur in the glass phase. The
latter secondary minerals crystallized from the melt prior to
cooling and formation of the glass phase. FIG. 4 shows a remnant
primary quartz grain with rounded edges indicating dissolution of
its formerly angular grain boundaries (31). The nearly complete
melting of most other primary mineral constituents of the original
feedstock components such as feldspar leaves little evidence of
their existence in this synthetic rock other than mottled areas
that retain the chemical signature of the parent mineralogy
(32).
[0066] The glass phase (33) with an aluminosilicate composition
contains trace amounts of cations such as potassium, calcium,
sodium, magnesium, and iron (33). EDS microchemical analysis of the
glass throughout the ceramic indicates that the glass composition
is heterogeneous and varies with respect to the aluminum:silicon
ratio as well as the trace cation content (34).
[0067] The newly formed (secondary) crystallite comprises the
crystalline phase of this synthetic rock. The longer processing
time resulted in secondary crystallites comprising 40-50% of the
volume of this material. The crystallites appear in two
recognizable morphologies each with distinct chemistries as
determined by EDS. Some crystallites appear in narrow lath and
skeletal shapes and occur singly and in clusters (35). Crystallites
of this morphology uniformly possess a chemistry most similar to
the bronzite species of pyroxene having high magnesium but low
calcium and iron contents (35). The size of the lath shaped
crystallites ranges from 1 to 3 .mu.m in width and from 5 to 25
.mu.m in length.
[0068] The other common morphology of crystallites is an equant
blocky shape similarly occurring singly and in clusters (36). This
latter crystallite morphology is associated with calcium to iron
ratios similar to augite or pigeonite varieties of pyroxene having
high calcium but low iron contents. The size of these blocky
crystallites ranges from 4 to 15 .mu.m.
[0069] The continuous glass phase in this synthetic rock material
leaves widely spaced isolated voids with little or no communication
between them resulting in very low absorption values (37).
The Second Embodiment
[0070] This embodiment is a method of processing mine tailings
employing a fast cooling schedule, which results in Applicant's
composition and corresponding articles of manufacture.
Example 2
[0071] A sample of tailings from the Idaho-Maryland gold mine,
having the general composition shown in Table 1, was air-dried to
less than 3% moisture and screened to remove material larger than
516 microns (30 mesh). The raw tailings material was calcined in
air at 900 degrees C. Following calcining, the material, without
additives, was mechanically compacted using a ram at a pressure of
approximately 300 psi within a nitride-bonded-silicon-carbide
process tube at a temperature of 1140 degrees C., with a residence
time of approximately 6 hours at temperature. The material was then
extruded through a rectangular die (15.2 by 1.3 cm) with a land
length of 3.5 cm, and subsequently cooled at a rate of about 10 to
20 degrees C. per minute, forming a synthetic rock hybrid material.
Test specimens of the resulting synthetic rock hybrid material had
an average modulus of rupture of about 42 MPa (6060 psi), and an
average water absorption of about 3.2% as determined by method ASTM
C373. Other resulting data are shown in Table 2.
[0072] FIG. 5 shows the scanning electron microprobe back-scattered
electron (BSE) image of the resulting synthetic rock hybrid
material. FIG. 5 illustrates the three characteristic phases
typical of the unique microfabric of this synthetic rock material.
These three phases include clasts (partially dissolved remnant
primary grains of the tailings feedstock); a glass phase derived
from the partial melting of primary mineral grains; and a secondary
crystalline phase comprised of similarly sized crystallites
enveloped in the glass phase. The latter secondary minerals
crystallized from the melt during cooling, likely prior to the
formation of the glass phase. FIG. 5 shows a remnant primary quartz
grain with rounded edges indicating dissolution of its formerly
angular grain boundaries (41). The nearly complete melting of most
other primary mineral constituents of the original feedstock
components leaves little evidence of their existence in this
synthetic rock.
[0073] The glass phase (42) with an aluminosilicate composition
contains trace amounts of cations such as potassium, calcium,
sodium, magnesium, and iron (42). EDS microchemical analysis of the
glass throughout the ceramic indicates that the glass composition
is heterogeneous and varies with respect to the aluminum:silicon
ratio as well as the trace cation content (43).
[0074] Four newly formed secondary crystalline phases are apparent
in this synthetic rock material including two distinct pyroxene
types, anhydrite and ilmanite. Pyroxene crystallites appear in two
morphologies each with distinct chemistries as determined by EDS.
One pyroxene crystallite morphology is a narrow lath shape (44).
The lath type pyroxenes uniformly possess a chemistry most similar
to the bronzite species having high magnesium but low calcium and
iron contents (44). The crystallite sizes range from 1.5 to 3 .mu.m
in width and from 5 to 50 .mu.m in length. The faster processing
time to produce this material (relative to Example 1) prevented
complex cluster development of the crystallites. Other pyroxene
crystallites occur with an equant blocky shaped morphology (45).
This latter type pyroxene occurs singly and in simple clusters.
This latter pyroxene crystallite morphology is associated with
calcium to iron ratios similar to augite or pigeonite varieties
with high calcium but low iron contents. The blocky crystallites
range from 1 to 5 .mu.m.
[0075] Sulfur in this synthetic rock has combined with calcium to
form crystallite clusters of anhydrite (46). Individual
crystallites within the clusters range from 2 to 7 .mu.m in
size.
[0076] Small similarly sized crystallites of ilmanite (iron
titanium oxide) of 1 to 5 .mu.m in size appear randomly arranged in
the glassy matrix (47).
[0077] The continuous glass phase in this synthetic rock material
leaves few and widely spaced isolated voids (48) with little or no
communication between them, resulting in very low absorption
values.
The Third Embodiment
[0078] This embodiment is a method of processing metavolcanic mine
development rock employing a fast cooling schedule, which results
in Applicant's composition and corresponding articles of
manufacture.
Example 3
[0079] A composite of drill-core samples taken from metavolcanic
(andesite, dacite, diabase, and others) rock from the
Idaho-Maryland mine ("development rock") was air-dried to less than
3% moisture, and ground to a size fine enough to pass 100% through
a 516-micron (30-mesh) screen. The development rock powder had a
composition as shown in Table 1. The development rock powder,
without additives, was processed through the apparatus described in
U.S. Pat. No. 6,547,550 (Guenther) at a temperature of 1160 degrees
C., with a mechanical pressure oscillating between about 160 psi
and 30 psi with a period of oscillation of 10 minutes, in a partial
vacuum atmosphere (about 170 mbar absolute pressure), with a
residence time of about 60 minutes before extruding the
consolidated plug of synthetic rock hybrid material. Following the
extrusion, the plug was cooled at a rate of about 5 to 15 degrees
C. per minute. Test specimens of the resulting synthetic rock
hybrid material had an average modulus of rupture of about 64 MPa
(9280 psi), and an average water absorption of about 0.8% as
determined by method ASTM C373. Other resulting data are shown in
Table 2.
[0080] FIG. 6 is the scanning electron microprobe back-scattered
electron (BSE) image of the resulting synthetic rock material from
composite Idaho Maryland development rock feedstock. FIG. 6
illustrates the three characteristic phases typical of the unique
microfabric of this synthetic rock material that collectively
comprise an aggregate (or breccia) arrangement. These three phases
include partially dissolved remnant primary grains of the original
metavolcanic feedstock constituents; a glass phase derived from the
partial melting of primary mineral grains; and secondary
crystalline phases comprised of similarly sized crystallites
enveloped in the glass phase. The latter secondary minerals
crystallized from the melt during cooling, likely prior to the
formation of the glass phase. FIG. 6 shows numerous remnant grains
of a variety of primary constituents forming a relatively coarse
clasts fraction. These primary lithic grains include polymineralic
metavolcanic rock fragments (51) and monomineralic mineral grains
(52). Specific minerals that occur either in monomineralic grains
comprised of a single mineral or polymineralic rock fragments
comprised of multiple minerals include plagioclase feldspar (53);
pyroxene (54); and remnants of degraded chlorite (55). Other
primary minerals inherited from the feedstock constituents that
also occur but not illustrated in FIG. 6 include sphene, quartz and
hematite.
[0081] The partial melting of feldspar (53) occurring in the
metavolcanic feedstock contributes to the formation of a melt phase
that created a glass matrix upon cooling (56). The rounded feldspar
grain margins indicate dissolution or melting of its formerly
angular grain boundaries. The glass phase (56) with an
aluminosilicate composition contains trace amounts of cations such
as potassium, calcium, sodium, magnesium, and iron. EDS
microchemical analysis of the glass throughout the ceramic
indicates that the glass composition is heterogeneous and varies
with respect to the aluminum:silicon ratio as well as the trace
cation content (57).
[0082] FIG. 6 illustrates the formation of the dominant secondary
crystalline phase that crystallized from the melt. Clusters of
pyroxene crystallites appear in various locations enveloped by the
glass phase (58). The individual pyroxene crystallites within the
clusters possess an equant blocky morphology with calcium to iron
ratios similar to augite or pigeonite varieties. Other secondary
minerals that crystallized from the melt but not illustrated in
FIG. 6 include maghemite (spinel group) and ilmanite (iron titanium
oxide).
[0083] The continuous glass phase of this synthetic rock material
envelops nearly the entire grain margin of the clasts resulting in
widely spaced isolated voids (59). There is little or no
communication between the isolated voids resulting in the very low
absorption values determined for this synthetic rock hybrid
material.
[0084] The unique structural attribute of this synthetic rock
material is the aggregate breccia microfabric created by the three
important components that includes 1) the primary remnant clasts,
2) the glass phase, and 3) the secondary crystallite phase. This
aggregate breccia structural arrangement of components (or
constituents) creates a strong aggregate microfabric with superior
strength and durability properties unique to this synthetic rock
material.
The Fourth Embodiment
[0085] This embodiment is a method of processing coal fly ash
employing a fast cooling schedule, which results in Applicant's
composition and corresponding articles of manufacture.
Example 4
[0086] Coal fly ash material was obtained from a coal power plant,
specifically Valmy train 2 in Winnemucca, Nev. The composition of
the raw material is shown in Table 1. The material was air-dried to
less than 3% moisture, and screened to pass 100% through a
516-micron (30-mesh) screen. Following calcining, the calcined coal
fly ash material, without additives, was mechanically compacted
using a ram at a pressure of approximately 300 psi within a
nitride-bonded-silicon-carbide process tube at a temperature of
1115 degrees C., with a residence time of approximately 10 hours at
temperature. The material was then extruded through a cylindrical
die, and subsequently cooled at a rate of about 10 to 20 degrees C.
per minute, forming a synthetic rock hybrid material. Test,
specimens of the resulting synthetic rock hybrid material had an
average modulus of rupture of about 57 MPa (8230 psi), and an
average water absorption of about 0.7% as determined by method ASTM
C373. Other resulting data are shown in Table 2.
[0087] FIG. 7 is the scanning electron microprobe back-scattered
electron (BSE) image of the synthetic rock material fabricated from
coal fly ash waste material feedstock. FIG. 7 illustrates the three
characteristic phases typical of the unique microfabric of this
synthetic rock material that collectively comprise an aggregate
structural arrangement. These three phases include clasts of
partially dissolved remnant primary grains of the original fly-ash
feedstock constituents; a glass phase derived from the partial
melting of primary mineral and fly-ash grains; and secondary
crystalline phases comprised of similarly sized crystallites
enveloped in the glass phase. The latter secondary minerals
crystallized from the melt during cooling, likely prior to the
formation of the glass phase. FIG. 7 shows remnant grains of
primary constituents that remain in this synthetic rock including
quartz (61) and fly-ash glass spherules (62).
[0088] The partial melting of fly-ash glass spherules--the dominant
feedstock constituent--created a melt phase that formed a
continuous glass matrix upon cooling (63). The glass phase (63)
with an aluminosilicate composition contains trace amounts of
cations such as potassium, calcium, sodium, magnesium, and iron.
EDS microchemical analysis of the glass throughout the ceramic
indicates that the glass composition is heterogeneous and varies
with respect to the aluminum:silicon ratio as well as the trace
cation content (64).
[0089] FIG. 7 illustrates the formation of up to four secondary
crystalline phases that crystallized from the melt during the
cooling process. These secondary crystalline phases include:
clusters of wollastonite crystallites (65) some of which nucleated
on remnant primary quartz grains (61); lath-shaped plagioclase
feldspar (66) and pyroxene (67) crystallites randomly distributed
in the glass phase; and blocky anhydrite crystallites (calcium
sulfate) not shown in FIG. 7. The anhydrite phase is a major
component of this synthetic rock material and serves as a major
receptacle for the sulfur that was a dominant constituent of the
coal fly-ash waste material.
[0090] Individual wollastonite crystallites range in size from 1 to
6 .mu.m. The lath shaped plagioclase and pyroxene crystallites
range from 1 to 5 .mu.m in width and 2 to 15 .mu.m in length. The
larger blocky anhydrite phenocrysts are a size that can be resolved
with the polarized light microscope with typical sizes ranging from
10 to 70 .mu.m.
[0091] The continuous glass phase of this synthetic rock material
envelops the entire grain margin of the primary and secondary
mineral grains resulting in few if any isolated voids (68). The
predominant void space in this synthetic rock was inherited and
associated with the primary fly-ash spherules (69). There is little
or no communication between any of the isolated voids resulting in
the very low absorption values determined for this synthetic rock
material.
[0092] The unique structural attribute of this synthetic rock
material is the aggregate breccia microfabric created by the three
important components that includes 1) the primary remnant clasts,
which in this example include mineral grains and mineraloid grains
such as glassy fly-ash spherules, 2) the glass phase, and 3) the
secondary crystallite phase. The cluster development of the large
wollastonite crystallites the crystallized around primary quartz
grains contributes to the coarse aggregate fraction (65). This
aggregate breccia structural arrangement of components (or
constituents) creates a strong aggregate microfabric with superior
strength and durability properties unique to this synthetic rock
material.
The Fifth Embodiment
[0093] This embodiment is a method of processing waste mineral
materials such as mine tailings, ash, slag, slimes, and the like,
which results in Applicant's composition and corresponding articles
of manufacture.
[0094] Referring to FIG. 8, raw material for synthetic hybrid rock
manufacture 100, may be for example mine tailings, waste rock,
quarry fines, slimes, fly ash, bottom ash, coal ash, incinerator
ash, wood ash, slag, or blends of these materials with each other
or with pure ceramic feed materials such as clay, feldspar, quartz,
talc, and the like. Silicate waste materials are particularly
well-suited for use as raw material. Raw material 100 is delivered
to screening apparatus 120, which has an outlet 121 for oversize
particles 122 with a size larger than a predetermined screen
opening size, and which further has an outlet 123 for undersize
particles 124 with a size smaller than a predetermined screen
opening size. Oversize particles 122 may be recycled to screening
apparatus 120 via a grinding process (not shown), or disposed
of.
[0095] Undersize particles of raw material 124 are conveyed to a
hopper 131 of rotary calciner 130. Feed auger 137 is driven, for
example by motor 136, and particulate raw material is thereby
conveyed to a heated rotating barrel 132. Barrel 132 is heated by
any of various means including but not limited to electric
resistance heaters, gas burners, and exhaust or waste heat from
other processes. Drive 139 rotates barrel 132, which may have a
smooth interior surface, or alternatively may have a surface that
is corrugated or otherwise roughened, for example with lifters, to
provide a means for the material to be repeatedly lifted and
dropped as it moves through the barrel. Barrel 132 is inclined at a
shallow angle from horizontal in order to slowly drive the powder
toward the discharge assembly 133. Calciner 130 optionally has gas
inlet 135 for the addition of air or other gases and vent 134 for
the removal of combustion products or other gaseous decomposition
products. Calciner 130 is operated at temperatures below the point
where the material begins to soften and sinter, but at elevated
temperatures such that the material is preheated and dried. Other
useful chemical transformations can be carried out in the calciner,
including but not limited to combustion of organic materials,
conversion of hydrated minerals to dehydrated oxides,
desulphurization, decomposition of carbonates, and the like. The
process temperature for each of these operations varies, but is
generally in the range of 100 to 1000 degrees Celsius.
[0096] Calcined particulate material 139 exits at a temperature
within this range, preferably about 800 to 1000 degrees Celsius,
and passes through valve 140 to hopper 150. Valve 140 can be closed
to provide a vacuum-tight seal between hopper 150 and calciner 130.
Preferably valve 140 is a high-temperature rotary valve that can
continuously flow material through while maintaining a pressure
differential.
[0097] Hopper 150 is preferably thermally insulated, or
alternatively provide with a source of heat to maintain the
temperature of particulate material. Vacuum outlet 151 may be
provided for connection to vacuum 152. Vacuum removes entrained and
interstitial gas from particulate material and contributes to the
production of void-free synthetic hybrid rock material from a
subsequent extrusion step. Vacuum can also reduce the oxidation of
minerals and can increase the variety or level of crystallization
in the resulting product.
[0098] Outlet 61 of hopper 150 is connected to feeder 160 at inlet
flange 161. Feeder 160 may function as a reciprocating ram, or as
an auger, or as both. Auger 162 is rotated by shall 163 and drive
164, thereby conveying particulate synthetic hybrid rock material
forward into extruder barrel 180. The entire auger/drive assembly
may be moved axially, for example by means of hydraulic ram 165
moving axially in hydraulic cylinder 166 due to pressure created by
pump or hydraulic power unit 167. The axial motion of auger 162
also conveys particulate material into extruder barrel 180.
[0099] A typical operation cycle for using both auger and ram
aspects of the invention together is as follows. Under little, or
none, or perhaps backward force from the hydraulic ram 165, drive
164 rotates auger 162, which conveys particulate material into
extruder barrel 180. When the available space in extruder barrel
180 is filled with newly conveyed particulate material, drive 164
is shut down and auger 162 stops rotating. Ram 165 is then
energized by power unit 167 to provide an axial force on auger 162,
which in turn pushes on material in extruder barrel 180. Material
is conveyed axially down extruder barrel 180 in this manner for a
predetermined distance. Once said predetermined distance has been
reached, the force applied by hydraulic ram is reduced, and the
cycle may be repeated.
[0100] Extruder barrel 180 may be constructed from a material with
excellent resistance to high temperatures, good thermal
conductivity, acceptable strength, and excellent resistance to
wetting by or reaction with materials to be processed in the
extruder. Preferably, extruder barrel 180 is constructed from
silicon carbide (SiC). Most preferably, extruder barrel 180 is
constructed from nitride-bonded silicon carbide (SIN--SiC), for
example Advancer.TM. material available from St. Gobain Industrial
Ceramics.
[0101] Extruder barrel 180 is compressed between feeder 160 and
spider 190 and supported within furnace 170. Furnace 170 provides
heat, for example by electrical resistance heaters or by gas
combustion, and is preferably a split-tube design for ease of
maintenance, and also preferably has multiple zones of temperature
control along its length. Furnace 170 provides heat to increase the
temperature of extruder barrel 180 high enough to fuse, sinter,
partially melt, or otherwise accomplish the desired vitrification
of the material within.
[0102] Within extruder barrel 180, particulate material fed by
feeder 160 is conveyed axially toward reducer die 181 and heated,
thereby consolidating and vitrifying particulate material into at
least partially molten synthetic hybrid rock material.
[0103] Reducer die 181 connected to the end of extruder barrel 180
provides a resistance to the flow of said at least partially molten
synthetic hybrid rock material and thereby increases the necessary
pressure applied by ram 165 to convey the material, providing a
mechanism for consolidation of the material. Optional land die 182
connected to the end of reducer die 181 may further increase the
resistance to flow. In the absence of land die 182, a spacer may be
used, for example an additional short length of barrel similar to
extruder barrel 180. At the discharge end of the extruder, that is
where the land die or spacer exits furnace 170, an insulator ring
183 made of strong, thermally insulating material, preferably
zirconia, is placed. Insulator ring 183 minimizes heat conduction
from the furnace to spider 190, and is captured in a recessed
opening within spider 190.
[0104] Spider 190 is a stiff plate that allows passage of extruded
synthetic hybrid rock product 130 through a hole in the center
while providing mechanical compression to insulator ring 183, land
die 182, reducer die 181 and extruder barrel 180. Spider 190 is
supported by a plurality of stiff springs 191, each reacting
against a load cell 192 mounted on a fixed rigid support.
[0105] Extruded synthetic hybrid rock product 130 exits land die
182, proceeds through insulator ring 183 and spider 190, and is
supported and conveyed by a plurality of rollers 201 within heated
chambers 200 and 220. The temperature in heated chambers 200 and
220 is maintained such that extruded synthetic hybrid rock material
230 remains deformable enough to be cut by cutters 210 attached to
actuators 212. After cutting, extruded synthetic hybrid rock
material 230 may be removed from heated chamber 220 and cooled by
various means to produce useful products. Alternatively, extruded
synthetic hybrid rock material 230 may be conveyed to subsequent
operations such as pressing, forming, rolling, molding, or glazing
at a high temperature, thereby efficiently using the heat in the
material.
* * * * *